Question

Glycine is a highly conserved amino acid residue in proteins (i.e., it is found in the same position in the primary structure of related proteins). Suggest a reason why this might occur.

Short answer

Glycine is highly conserved because its small size and flexibility are essential for tight turns and proper protein folding.

Step-by-step solution

Introduction to Glycine

Understand the unique properties of glycine: It is the smallest amino acid, with a single hydrogen atom as its side chain.

Impact on Protein Structure

Glycine’s small size allows it to fit into tight spaces within the protein structure, making it essential in regions where space is constrained.

Flexibility Contribution

Glycine provides flexibility to protein chains because it has no side chain that could sterically hinder movement, allowing sharper bends or turns.

Functional Importance

Glycine’s ability to fit into tight turns and provide flexibility is critical for the proper folding and function of proteins, especially those with intricate structures.

Evolutionary Conservation

Proteins that require flexibility or tight turns as part of their function will conserve glycine at critical positions, explaining why it remains highly conserved across related proteins.

Key concepts

Amino Acids

Amino acids are the building blocks of proteins. They are organic molecules that contain both amino and carboxyl functional groups. There are 20 standard amino acids found in proteins, each with a unique side chain, or R group, that determines its properties.
Glycine is one of these amino acids. Unlike other amino acids, glycine has the simplest structure. Its side chain is just a hydrogen atom.
This simplicity gives glycine unique properties that are crucial for protein function.

Protein Structure

Proteins are complex molecules that perform a vast array of functions within organisms. They are composed of long chains of amino acids, folded into specific three-dimensional shapes.
Glycine plays a significant role in this structure due to its small size. It can fit into tight spaces within the protein's architecture, which is crucial in regions where space is limited.
Without glycine, proteins might not fold correctly, leading to loss of function.

Evolutionary Biology

Evolutionary biology studies how organisms evolve over time. A key concept in this field is evolutionary conservation, where certain traits or sequences remain unchanged across different species.
Glycine is highly conserved in protein sequences because of its critical role in maintaining protein structure and function. Natural selection favors the conservation of glycine in proteins that need flexibility or tight turns.
This conservation highlights glycine's importance in the evolution and adaptation of organisms.

Protein Flexibility

Protein flexibility refers to the ability of protein structures to adopt multiple conformations. Flexibility is important for many protein functions, including enzyme activity and signal transduction.
Glycine's small size and lack of a bulky side chain allow it to provide this flexibility. It can enable sharper bends and turns in the protein chain, facilitating dynamic movements and conformational changes.
This flexibility can be essential for proteins that undergo frequent structural adjustments.

Protein Folding

Protein folding is the process by which a protein chain acquires its functional three-dimensional shape. Proper folding is essential for protein function.
Glycine contributes significantly to protein folding by fitting into tight turns and loops, stabilizing the structure where space is constrained.
Misfolding can lead to diseases, making glycine's role in proper protein folding crucial for maintaining health and preventing disorders.